Supporting head for abrasive disks



Nov. 23, 1948. E. H. TOTT SUPPORTI-NG HEAD FOR- ABRAsIvE DIsKS Filed Dec. 25, 1946 Patented Nov. 23,21948 U N I T E D s TAT-Es l SUPPORTING' HED FOR ABRASIVE DISKS 'EdwirnlrLv xTott, -San Leandros Calif;

. Application"DecembeZB, 1946,. SerlalN'.".71'{79'0"1 'This invention relates `to abrasive diskf'grindersof the hand operated type,` and more particu` larly to a supporting head for abrasive disks.

Due to their relatively high degree of flexibility, abrasive disks are associated with a lseparate backing plate so that the requisite support is provided forithe disk. lBoth disk and plate are conventionally seated on a supporting head and secured forrotation therewith to prevent relative movement of the disk and plate during a grinding operation.

YWhen the rotating disk and plate combination is snagged o-nlthe work, as frequently occurs, the abrasive disk, being rather easilytearable, may have a portion ripped therefrom, buttheibacking p1ate,secured for rotation With the diskand being of a relatively tough material, such `as moulded and impregnated ber, will not `ordinarily tear when snagged. Consequently, asnagging of av backing plate often results inawrenching of the grinder from'the hands ofthe opera'- tor with'attendant injuries to the operator inthe event thathe is struckzby the whirling disk.

The instant invention has for its primaryzobject the provision of a supporting yhead for-a grinder whereby the abrasive disk zandbacking plate are relatively rotatable. Y

This and other Lobjects of the invention are preferably achieved by providing a supporting head having a backing plate seated thereon so as to be in-sligh't frictional engagementwith the abrasive disk and the supporting head, said engagement being suiiicient to cause the backing plate to rotate with the disk during normal operation of the grinder. The snagging of the backing plate is, however, effective to stop the rotation of said plate while allowing the normal-rotation of the abrasive disk and supportinghead. Thus, the aforedescribed wrenching of the grinder from the operators hands due to the snagging of the backing plate is obviated.

Other objects and advantages of the invention Will be apparent from the following description when taken in conjunction with the drawing forming part of this specication, and in which:

Figure 1 isl a View in section through the gear case of a hand grinder embodying the supporting head of the invention; and

'Figure 2 is an exploded view in perspective of thesupporting head and an abrasive disk and backing plate.

lReferring to the drawing for more specific details of the invention,'l indicates generally a gear case of'a hand'grinder, said case :having'a tool spindle IZjOurnaIled for rotationin bearings '10 Claims. (CIJ. y51--3129'7 121 l4`=and ifili. `"""1`h"'` spin'dle 112i isrprovidedfexteriorly of the gear case with a boss I'll-and aftlireaded en'd-portion I 8, '-andinteriorly of l the A-gear case there "-ls keyed toi the spindle vafgear carrier 2`0f hel"v against the' bearing |4 by-af lock-nut l"22a 1A faceygear 24 is 1 heldl against the *gear carrier 122 by a-'spr'ing 25 abutting'- a spring retainer i281, -Jand said gear is locked for rotationlfwithlthefgear carrier '22* by a drivepinsf30l *Thefface gear *24 islin* mesh '-Withf'ai pinionge'ar* 32'fkeye`d' to a shaft 34-adapte`d to be driven by ai motor armature; not showin-*1'It*isapparent thatthe rotationfof the motor armature is effective-'to :drive i the spindle lf2" throughfthe?medium` of #shaft f34," pinion'gear 32, face gear 24, and gear carrier `l^20`secured`fto` the spindle I2.

The above described-"grinder structure is '-conventiorlal, -andis included for the purposefof illustratingthe lrelative `proximity of the grinderv gear system'to the supporting head, hereinafter' described.

'A supporting head, indicated generally atfSE, isfcomprised iota cylindrical hub i38fvhaving'a double diarnetral bore 40 therethrough, said hub being-provided witha plurality of'nsf42`, a-con.v cave*Ik face-Ml; and a fperipheralrshoulder -i46""`adjacent "said Iiiaee. 'A `backing"fplatedWhat/ing `a central`l` opening 15d-is supported-A fon' the Asl'lcmider 46;'andfan abrasive-disk;52fhaving aY centralopening'54 and an'annularinclined"portion 56 over# lies-thefbacking `platei with the portion "56 of -the disk in Iabutting relation to thereon-cave f face *My o the 2 hub#F 3BR'` V"The Y` lii-ibi138"`is secured `on the spindle l1'2'4 inengagementwvitnl theboss I 'l'L by a centering plug 58 ttinglintofthe largerdiametral portion lof-fthe' lcorel an'df threadablye'engaged with-'fthe endI portion i9y of the spit-idle; The plug 58 hasf a1ffl5nge`16ihavingf-an Uangu-larly incl-ined under-sidein pressing #engagement 'witli'tlie pore 1510x1756.of-:ltiieidiskiZt tosecur`e'-fthe disk `against relativefmcvein'ent with respect to= the hea d`-3 6".-

Wheni the fspindlef f2@ isfdriven to rotate the supportingrhea'd-BB and `the 'abrasiveV disk secured thereto, `-thebacking"plate is' normallyr rotatefdfby a *slight frictional 'engagement betweenftl'ie yplate and the'disk=52 lvandhub yi138. ""HoWeverfthe-rota-f tion of theibacking-'platetnrayf 4belprevented by the applicationlof-l a- 'slightho'lding' 'force 'tol-the plate* Without aictingfthevrotationj ofitlietdiskrEZ* and hfead': The plateM-may; thereorebesnagged with" no* dan-gerj ofcausing a uwrenclrlirrg of the grinderfromttiie hands; ofL theroperatorl Duringithe'operationof' the grinder; thepinion geartzffacefgear lwand/` geartcarrieriz becomel heated;` and the iproxii'nityof 4"these"driving lel 3 ments in the gear case l to the supporting head 36 allows for a ready transfer of heat to the spindle l2 and a consequent rise in the temperature of the supporting head. An appreciable rise in temperature of the head 36, which would occur after extended operation of the grinder, would normally be sufficient to enhance the frictional engagement between the backing plate 48 and the head 36Vand disk 52, due to a slight expansion of the head 36 and that portion of the backing plate in engagement with the head 36 and disk 52, to a point where a holding force applied to the plate would not be effective to stop the rotation of the plate. Y

In order to insure that slippagebetween the backing plate and the abrasive disk will obtain in the event that a holding force is applied to the plate, the fins 42 are provided in the head 36 to a cylindrical hub having a centrally disposed passage therein, a centering plug receivable within said passage and securable to the grinder spindle, a flange on said plug to secure an abrasive disk to the end surface of the hub, and an annular shoulder inset from said end surface of the hub dissipate heat therefrom. Thus, the ns 42 coact With the shoulder 46 of the head 36 to provide for relative rotation between the abrasive disk and thebacking plate.

The supporting head 36 is preferably made of aluminum for lightness, and it is to be pointed out that the provision of the ns 42 materially reduces the weight of the head, thereby decreasing the effort on the part of the operator in manipulating the grinder. v l

, While the preferred embodiment of the invention has been shown and described, it is understood that the embodiment is subject to modification within the spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a grinder device having a spindle, power means to rotate said spindle, a hub secured to the spindle for rotation therewith, an abrasive disk secured to the hub for rotation therewith, and a backing plate mounted on said hubin juxtaposition to said disk, the improvement comprising` means embodied in the hub adapted to seat said backing plate for free slippage with respect to said hub. f

2. In a grinder device having a spindle, powe means to rotate said spindle, a hub secured to the spindle for rotation therewith, an abrasive disk secured to the hub for rotation therewith, and a backing plate mounted on said hub in juxtaposition to said disk, the improvement comprising means formed in the face of said hub adaptedto seat said backing plate in engagement with said abrasive disk for free rotary slippage with respect to said hub and the disk upon the application of a holding force to said plate.

3. In a grinder device having a spindle, `power means to rotate said spindle, a hub secured to the spindle for rotation therewith, an abrasive disk secured to the hub for rotation therewith, and a backing plate mounted on saidhub in juxtaposition to said disk, the improvement comprising means forming an annular seat in the face of said hub for mounting the backing plate thereon in juxtaposition to said disk for free rotation with said disk and for non-rotation therewith upon the application of a holding force to said plate, and heat dissipating means formed in said hub to dissipate heat received from the spindle and prevent plate-gripping expansion of said hub.

4. In a grinder device having a spindle, power means to rotate said spindle, a hub secured to the spindle for rotation therewith, an abrasive disk secured to the hub for rotation therewith, and a backing plate mounted on said hub in juxtaposition to said disk, thevv improvement comprising an Y nular shoulder inset from said end surface of thehub to freely mount a backing plate thereon, and a plurality of cooling ns carried by said head to cool the said head to prevent plate-gripping expansion thereof due to heat received from said spindle, whereby the free mounting of the backing plate may be maintained.

'7. A grinder device supporting head comprising a cylindrical hub having a concave end surface and a centrally disposed passage therethrough, a centering plug receivable within said passage and securable to the grinder spindle, a flange on said plug having an under surface complementary to the concave end surface of the hub, said flange being adapted to secure an abrasive disk to said end surface of the hub, and an annular shoulder on said hub inset from the outeredge of said end surface, said shoulder being adapted to freely mount a backing plate thereon in non-gripping engagement with said hub whereby said plate may be turned or rotated while the hub is stationary.

8. A grinder device supporting head comprising a cylindrical hub having a concave end surface and a centrally disposed passage therethrough, a centering plug receivable within said passage and securable to the grinder spindle, a flange on said plug having an under surface complementary to the concave end surface of the hub, said flange being adapted to secure an abrasive disk to said end surface of the hub, an annular shoulder on said hub inset from the outer edge of said end surface, said shoulder Ibeing adapted to freely mount a backing plate thereon, in non-gripping engagement with said hub whereby said plate is capable of relative rotation with respect to said hub and a plurality of spaced cooling fins on said hub to dissipate heat therefrom received from said spindle to maintain the backing plate relatively rotatable with respect to the hub and disk by preventing plate-gripping expansion of said hub.

9. A grinder device supporting head comprising a hub having an axially disposed passage therethrough, a centering plug receivable within said passage and securable to a grinder spindle, a flange on said plug to secure an abrasive disk to the end surface of the hub, and an annular shoulder inset from said end surface and located fully outwardly of said plug flange for the free mounting of a backing plate thereon in juxtaposition to said disk.

10. A grinder device supporting head comprising a hub having an axially disposed passage therethrough, a centering plug receivable within said passage and securable to the reduced diametrical end portion of a rotatable grinder spindle, said plug having a peripheral flange adapted to clamp an abrasive disk to the forward end surface of the hub and to clamp the rearward end surface of the hub in pressing engagement with a shoulder on said spindle upon the securing of said plug to said spindle to prevent relative movement between the hub, disk and spindle elements, and an annular shoulder inset from the forward end surface of said hub and located outwardly of said plug flange, said shoulder being adapted to freely seat a backing plate thereon in juxtaposition to the disk so 6 that said backing plate may be stopped against rotation during rotation of said hub and disk.

EDWIN H. TOTT.

REFERENCES CITED The following references are of record in the le of this patent:

10 UNITED STATES PATENTS Number Name Date 1,693,163 Schacht Nov. 27, 1928 1,882,693 Albertson et al. Oct. 18, 1932 2,104,147 Anderson Jan. 4, 1938 15 2,132,917 Albertson Oct. 1l, 1938 FOREIGN PATENTS Number Country Date 329,323 Great; Britain May 14, 1930 

